Entryway systems used in residential and commercial buildings include single and double door assemblies having one or more sidelights or sidelight panels flanking the door(s). Such entryway systems are typically fabricated using vertical mullions or mull posts positioned between the door(s) and the associated sidelight or sidelight panel to connect the structures. When these entryway systems are used in coastal regions of the country, it is desirable that the systems be capable of withstanding the extremely high pressures caused by high winds as well as impacts caused by flying debris.
Traditionally, mull posts have been fabricated from wood, such as pine, small pieces of which are finger jointed end to end and milled to form the mull profile. While such construction is acceptable in many regions, it generally does not result in mull posts that can withstand the extreme weather conditions that often occur in coastal areas. For instance, when an entryway having traditional wood mull posts is exposed to the high pressures from wind forces that entryways in coastal areas may experience, the forces transferred through the door to the mull posts can cause the mulls, and thus the entryway, to fail. Often the mulls break apart at the finger joints that are used to join the small segments of mull together. Even where the finger joints hold, the wood of the mulls can split apart along the grain at the locations of door hardware such as the strike plate, deadbolt strike, and hinges. Further, the high pressure can cause the mulls to deflect or bend, compromising the integrity of hardware fasteners. Thus, traditional finger jointed wood mull posts are not acceptable for use in regions with stringent design pressure requirements. Even where solid wood mull designs are used to eliminate failure at finger joint locations, problems caused by splitting of the wood along its grain remain.
More recently, extruded polymer mull posts made from inexpensive materials such as polyvinyl chloride (PVC) have been used. While polymer mull posts may not be as susceptible to breaking or splitting like traditional wood mulls, they still may be highly susceptible to deflection or bending when exposed to high pressure, thus compromising the integrity of the entryway system as previously explained.
In addition to the high design pressure requirements in hurricane prone regions, building codes in coastal regions also typically require that an entryway withstand a direct impact by airborne debris such as tree limbs. Traditional solid wood mull posts and extruded polymer mulls may be highly vulnerable to such impacts, again, for the reasons previously stated.
Thus, a need exists for an entryway system incorporating high strength mull posts that meet or exceed design requirements imposed by stringent building codes in coastal regions. Such mull posts should be inexpensive to produce, and should emulate the appearance of traditional wooden mulls so that they are acceptable for use in private residences.